Astronaut Bruce McCandless II using a
Manned Maneuvering Unit outside the Un-
ited States Space Shuttle Challenger in 1984.
An astronaut or cosmonaut
is a person
trained by a human spaceflight program to
command, pilot, or serve as a crew member
of a spacecraft. While generally reserved for
professional space travelers, the term is
sometimes applied to anyone who travels into
space, including scientists, politicians, journ-
alists, and tourists.
Until 2003, astronauts were sponsored
and trained exclusively by governments,
either by the military, or by civilian space
agencies. However, with the sub-orbital flight
the privately-funded SpaceShipOne in
2004, a new category of astronaut was cre-
ated: the commercial astronaut.
The criteria for what constitutes human
spaceflight vary. The Fédération Aéronaut-
ique Internationale (FAI) Sporting Code for
astronautics recognizes only flights that ex-
ceed an altitude of 100 kilometers (62 mi).
However, in the United States, professional,
military, and commercial astronauts who
travel above an altitude of 80 kilometers
(50 mi) are awarded astronaut wings.
Countries whose citizens have flown in space.
As of November 14, 2008, a total of 489
humans from 38 countries have reached
100 km or more in altitude, of which 486
reached Low Earth orbit or beyond. Of
these, 24 people have traveled beyond Low
Earth orbit, to either lunar or trans-lunar or-
bit or to the surface of the moon; three of the
Under the U. S. definition, 496 people
qualify as having reached space (above
50 miles (80 km) altitude). Of eight X-15 pi-
lots who reached 50 miles (80 km) or more in
seven reached above 50 miles
(80 km) but below 100 kilometers (about 62
miles). Space travelers have spent over
30,400 person-days (or a cumulative total of
over 83 years) in space, including over 100
astronaut-days of spacewalks. As of
2008, the man with the longest time in space
is Sergei K. Krikalev, who has